Simple untethered flagellated robot in fluids and granular media

Rotating flexible flagella have been ubiquitously adopted by cells, microorganisms, and soft robots for propulsion. We report a simple untethered flagellated robot that can swim in both granular media and fluids at low Reynolds number. The robot consists of a motor embedded in a cylindrical head and multiple flagella made of elastomeric rods. We experimentally analyze the effect of various physical parameters, such as angular speed of the motor, head size, tail length, and number of tails, on the performance of the robot. In parallel with experiments, we develop a numerical simulation tool for this fluid-structure interaction problem based on the discrete elastic rods algorithm (for the structures part) and resistive force theory (for the fluidic forces). The simulations are quantitatively compared with experimental data. The computational efficiency of the simulator can be leveraged for data-driven learning of the robot’s dynamics. It can also serve as a design tool to optimize the structural design of the robot.